What people don't realize is how much money casinos suck out of a local community. I've watched a lot of casinos and I have never seen a local economy improved by one. Your community paid for that park - many times over.
Do you mean people spent money at the casino instead of at the other area businesses? I'd can not deny that is happening. But, the casinos are already here and are not going to go away. The only thing that will go away is money dumped into the local community by the casinos if the measure passes.
Only one thing worse than a casino sucking money out of the local economy and putting some of it back. And that is the state sucking that money out and putting very little of it back.
Your point is valid only before the casinos arrived. That is, unless you are advocating they all be removed.